Cook fettucine according to package directions, reserving 1 cup of the pasta water; set aside. While pasta is cooking, add olive oil to a large pot over medium-high heat. Saute garlic for 1 minute, being careful not to burn the garlic. Add sun-dried tomatoes, diced tomatoes, tomato paste, and sugar, stirring until well combined. Reduce heat to medium-low and whisk in cream and sour cream. Let simmer and thicken for 5 minutes. Add spinach to sauce and cook until wilted. Add salt and pepper to taste. If sauce is too thick, use reserved pasta water to thin it out. Add pasta to prepared sauce and toss until coated.